Double-ceramic-layer thermal barrier coating and preparation method thereof

Abstract

The invention relates to the technical field of thermal barrier coating preparation, in particular to a double-ceramic-layer thermal barrier coating and a preparation method thereof. The double-ceramic-layer thermal barrier coating comprises a base body and further comprises a bonding layer, a ceramic middle layer and a ceramic top layer which are sequentially deposited on the base body, the ceramic middle layer and the ceramic top layer are both doped with pore-forming agents, and the pore-forming agents are aluminum oxide hollow microspheres. The aluminum oxide hollow microspheres are doped into the double ceramic layers to serve as a pore forming agent, the pore content is increased, meanwhile, the stability and the mechanical property of the coating structure are guaranteed, the high-temperature heat insulation performance of the coating structure is further improved due to the increased pore content, the ceramic layers can still keep stable at the temperature of 1400 DEG C or above, and the service life of the coating structure is prolonged. The obtained thermal barrier coating system can be used for hot end components of devices such as gas turbine engines, so that the heat energy loss is reduced, the kinetic energy efficiency is improved, and the service life is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of thermal barrier coating preparation, and in particular to a double-ceramic-layer thermal barrier coating and a preparation method thereof. Background Art

[0002] Gas turbine engines, as core power plants in aviation, energy, and other fields, have hot-end components (such as turbine blades) exposed to extreme environments exceeding 1300°C for long periods of time. Although the temperature resistance limit of high-temperature alloy substrates has been increased to 1150°C, further increases face material science bottlenecks. In this context, thermal barrier coatings (TBCs) technology has become a breakthrough solution: by depositing a ceramic insulation layer on the alloy surface, the substrate temperature can be reduced by 100-300°C, while allowing the gas temperature to rise to above 1600°C, significantly improving thermal efficiency.

[0003] Among TBCs, yttria-stabilized zirconia (YSZ) is widely used due to its excellent thermal shock resistance and low thermal conductivity (approximately 2.2 W / (m·K)) below 1200°C. However, when the service temperature exceeds 1200°C, YSZ undergoes a tetragonal to monoclinic phase transformation, accompanied by a volume expansion of approximately 3-5%, leading to cracking and even flaking of the coating. Furthermore, the sintering effect of YSZ at high temperatures reduces its porosity from an initial 15-20% to less than 5%, sharply deteriorating its thermal insulation properties.

[0004] Furthermore, the current mainstream structure of TBCs is a double-layer structure consisting of a ceramic top layer and an adhesive top layer. This structure is widely used due to its simple preparation process. However, the significant difference in thermal expansion coefficient and elastic modulus between the upper and lower layers of the double-layer structure leads to high thermal stress at the interface, which can cause coating failure. Furthermore, existing thermal barrier coatings generally suffer from technical deficiencies such as insufficient high-temperature phase stability, poor thermal shock resistance, limited thermal insulation performance, and susceptibility to oxidative corrosion.

[0005] With the development of TBCs technology, researchers have gradually realized the critical impact of pore structure on coating performance and have begun research on pore formation in thermal barrier coatings. Graphite is often used as a pore-forming agent in traditional TBCs, but it suffers from significant drawbacks during high-temperature plasma spraying: ① Severe porosity loss: Graphite decomposes at approximately 600°C, while the plasma jet temperature reaches 10,000-15,000°C. Experiments have shown that during the spraying process, the graphite completely burns and vaporizes, causing its theoretical porosity (calculated at a 20wt% addition) to plummet from the expected 25% to a measured value of ≤8%, resulting in a porosity loss of 68%. ② Pore structure degradation: CO2 gas generated by graphite decomposition forms irregular closed pores in the molten ceramic, resulting in a discrete pore size distribution and leading to thermal stress concentration.

[0006] Therefore, there is an urgent need to develop a new dual-ceramic layer thermal barrier coating and its preparation method to improve the high-temperature stability and thermal insulation performance of the thermal barrier coating system. Summary of the Invention

[0007] To achieve one of the above objectives, the present invention provides a dual-ceramic layer thermal barrier coating and a preparation method thereof, which improves the comprehensive performance of the thermal barrier coating through multi-layer structure design and pore gradient control.

[0008] The technical solution of the present invention is achieved as follows:

[0009] In a first aspect, the present invention provides a dual-ceramic layer thermal barrier coating, comprising a substrate, and also comprising an adhesive layer and a ceramic layer sequentially deposited on the substrate; the ceramic layer is doped with a pore-forming agent, and the pore-forming agent is hollow alumina microspheres.

[0010] Preferably, the ceramic layer includes a ceramic middle layer and a ceramic top layer, which are sequentially deposited on the bonding layer, and the thermal expansion coefficients of the substrate, bonding layer, ceramic middle layer and ceramic top layer are set in a gradient from large to small.

[0011] More preferably, the particle size of the alumina hollow microspheres is 50-100 μm. Too large a particle size will affect the mechanical properties of the coating, while too small a particle size will affect the thermal insulation performance of the coating.

[0012] Furthermore, preferably, the hollow alumina microspheres in the ceramic middle layer account for 2-5 wt% of the total amount of the ceramic middle layer; and the hollow alumina microspheres in the ceramic top layer account for 2-5 wt% of the total amount of the ceramic top layer. Excessive addition affects the mechanical properties of the coating, while too little addition affects the thermal insulation performance of the coating.

[0013] Preferably, the base material is a nickel-based high-temperature alloy, the bonding layer comprises a NiCrAlY alloy; the ceramic material of the ceramic intermediate layer comprises yttria-stabilized zirconia (YSZ); the ceramic material of the ceramic top layer comprises ytterbium aluminum garnet (YbAG, Yb3Al5O 12 ) or rare earth hexaaluminate ReMAl 11 O 19 One of the following, wherein Re includes one of La, Nd, Sm or Gd, and M includes one of Mg, Zn, and Mn.

[0014] More preferably, the particle size range of the powder is controlled by sieving, and the particle size of the NiCrAlY powder is 40-50 μm; the particle size of the YSZ is 50-100 μm; the Ytterbium aluminum garnet or ReMAl 11 O 19 The particle size of the powder is 35-125 μm.

[0015] Further preferably, the thickness of the bonding layer is 50-80 μm, the thickness of the ceramic middle layer is 100-150 μm, and the thickness of the ceramic top layer is 100-150 μm.

[0016] In a second aspect, the present invention relates to a method for preparing the above-mentioned dual-ceramic layer thermal barrier coating, comprising the following steps:

[0017] S1, pretreatment of substrate;

[0018] S2, depositing a bonding layer on the substrate;

[0019] S3, mixing a pore-forming agent with a ceramic material of a ceramic intermediate layer, and depositing a ceramic intermediate layer containing the pore-forming agent on the bonding layer;

[0020] S4. Mixing the pore-forming agent with the ceramic material of the ceramic top layer, and depositing the ceramic top layer containing the pore-forming agent on the ceramic middle layer to complete the preparation of the thermal barrier coating.

[0021] Preferably, the substrate pretreatment is: cutting and sandblasting the nickel-based high-temperature alloy material, followed by ultrasonic cleaning and drying.

[0022] Further preferably, the nickel-based high-temperature alloy is cut using an electric spark cutting machine, and the cutting size is 100 mm×50 mm×3 mm.

[0023] Further preferably, the sandblasting medium is 150-300 mesh corundum sand, and the compressed air pressure is 0.1-1 MPa.

[0024] Further preferably, the ultrasonic cleaning time is 5-15 minutes.

[0025] Preferably, in step S2, atmospheric plasma spraying technology is used to deposit a NiCrAlY bonding layer on the surface of the substrate.

[0026] Further preferably, in step S2, a plasma gas Ar / H2 mixed gas is used, wherein the Ar flow rate is 30-40 L / min, the H2 flow rate is 10-15 L / min, the spraying distance is 100-120 mm, the power is 40-45 kW, and the powder feeding rate is 5%-7%.

[0027] Preferably, in step S3, atmospheric plasma spraying technology is used to deposit a ceramic intermediate layer containing a pore-forming agent and whose ceramic material is YSZ on the surface of the substrate.

[0028] Further preferably, in step S3, a plasma gas Ar / H2 mixed gas is used, wherein the Ar flow rate is 30-40 L / min, the H2 flow rate is 10-15 L / min, the spraying distance is 100-120 mm, the power is 40-45 kW, and the powder feeding rate is 13%-16%.

[0029] Preferably, the ceramic material deposited on the substrate surface by atmospheric plasma spraying technology in step S4 is ytterbium aluminum garnet (YbAG, Yb3Al5O 12 ) or rare earth hexaaluminate ReMAl 11 O 19 The top layer of ceramic containing pore former.

[0030] Further preferably, in step S4, a plasma gas Ar / H2 mixed gas is used, wherein the Ar flow rate is 30-40 L / min, the H2 flow rate is 10-15 L / min, the spraying distance is 100-120 mm, the power is 30-35 kW, and the powder feeding rate is 13%-16%.

[0031] Compared with the prior art, the advantages of the present invention are:

[0032] (1) The present invention adds a ceramic top layer with better temperature resistance to the ceramic intermediate layer, and at the same time, a certain number of alumina hollow microspheres are added to the ceramic layer. The ceramic top layer can still remain stable above 1400°C, and the grain growth and sintering phenomena at high temperatures are not obvious. At the same time, the ceramic intermediate layer also plays a transitional role, so that the thermal expansion coefficient of each functional layer has a gradient from the substrate to the surface, thereby improving the high-temperature stability of the thermal barrier coating and thus extending the high-temperature service life.

[0033] (2) The present invention incorporates a pore-forming agent into both ceramic layers, increasing the pore content while also ensuring the stability of the coating structure and its mechanical properties. The increased pore content also further enhances its high-temperature thermal insulation performance. Furthermore, the hollow alumina microspheres used in the present invention are not easily melted at high temperatures, thus ensuring a high porosity.

[0034] (3) The production process of the present invention is relatively simple, and the pore-forming agent used is low-cost and abundant in source, allowing for scaled-up production. The thermal barrier coating system obtained by the present invention can be used for gas turbine power generation, increasing the turbine inlet temperature and improving power generation efficiency, protecting nuclear reactor metal pipes from high-temperature corrosion, and can be used for furnace linings and crucibles to extend the life of high-temperature furnaces and reduce heat loss. It can also be used for rocket engine turbine blades to reduce the blade surface temperature and significantly extend the life. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0036] Figure 1 This is a schematic structural diagram of a double-ceramic-layer thermal barrier coating prepared in Example 1 of the present invention;

[0037] In the figure, 1-substrate, 2-bonding layer, 3-ceramic layer, (3-1)-ceramic middle layer, (3-2)-ceramic top layer, 4-alumina hollow microspheres;

[0038] Figure 2 Schematic diagram of the structure and high-temperature thermal insulation performance of a double-ceramic-layer thermal barrier coating prepared in Example 1 of the present invention;

[0039] Figure 3 This is a comparison chart of the porosity changes of the double-ceramic-layer thermal barrier coatings prepared in Comparative Example 1 and Examples 1 to 4 of the present invention at different pore-forming agent dosages. DETAILED DESCRIPTION

[0040] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0041] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, features defined as "first" or "second" may explicitly or implicitly include one or more of such features. Furthermore, in the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0042] In this document, the terms “contain”, “include” or “include” are open expressions, that is, they include the contents specified in the present invention but do not exclude other contents.

[0043] As used herein, the terms "optionally," "optional," or "optionally" generally mean that the subsequently described event or circumstance may but need not occur, and that the description includes instances where the event or circumstance occurs and instances where it does not.

[0044] In view of the problems that the classic TBC material YSZ is prone to phase change and sintering at high temperatures, which seriously affects the service life of the coating; traditional pore-forming agents are easily vaporized at high temperatures to generate pores, and the raw materials will melt during the coating spraying process, thereby filling part of the pores generated by the pore-forming agent, resulting in a decrease in the porosity of the coating. The present invention provides a double-ceramic-layer thermal barrier coating.

[0045] First, considering that the thermal expansion coefficients of the bonding layer and the ceramic top layer are quite different, the inventors selected a ceramic middle layer as a transition layer and constructed a coating system with a gradient structure (along the direction from the substrate to the ceramic top layer) with a thermal expansion coefficient from large to small. At the same time, a certain number of hollow alumina microspheres were incorporated into the ceramic layer. The appropriate amount of pores can effectively reflect and scatter thermal radiation, reducing the transfer of heat to the substrate, thus forming a thermal barrier coating consisting of a bonding layer, a ceramic middle layer containing a pore-forming agent, and a ceramic top layer containing a pore-forming agent (along the direction from the substrate to the coating thickness).

[0046] Secondly, the addition of hollow alumina microspheres can reduce the oxidation rate of the thermal barrier coating, thereby improving the coating's antioxidant properties. Alumina hollow microspheres have high hardness and strength. When incorporated into the thermal barrier coating, when the coating is subjected to external forces, the microspheres can withstand a certain amount of pressure and disperse stress, thereby improving the coating's compressive strength and making it more difficult to be crushed or deformed. The presence of hollow alumina microspheres can hinder the penetration of oxygen and moisture, reducing chemical reactions and oxidation at the interface, and can also improve the coating's microstructure, making it denser. The dense microstructure can reduce cracks in the coating, thereby improving the coating's adhesion. The hollow microsphere pore former optimizes pore distribution and improves the thermal insulation temperature difference.

[0047] The following is a clear and complete description of the technical solutions in the embodiments of the present invention, in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0048] Example 1

[0049] This embodiment provides a double-ceramic layer thermal barrier coating, the structure of which is as follows: Figure 1 As shown, it includes the following components:

[0050] Substrate 1 is nickel-based high-temperature alloy, model GH3536;

[0051] Adhesive layer 2, NiCrAlY adhesive layer, 50 μm thick;

[0052] The ceramic intermediate layer 3-1 is a YSZ layer containing 2 wt% alumina hollow microspheres 4, with a thickness of 100 μm;

[0053] The top ceramic layer 3-2 is a YbAG layer containing 2 wt% alumina hollow microspheres 4, with a thickness of 100 μm;

[0054] The thermal expansion coefficient of each functional layer has a gradient from the substrate to the surface;

[0055] The particle size of the NiCrAlY powder used is 40 μm, the particle size of the YSZ powder used is 50 μm, the particle size of the YbAG powder used is 35 μm, and the particle size of the alumina hollow microspheres 4 used is 50 μm.

[0056] The specific preparation method is as follows:

[0057] Step 1: Powder preparation

[0058] (1) Preparation of YbAG powder: Yb2O3 and Al2O3 were mixed in a molar ratio of 3:5, placed in an air atmosphere, pre-calcined at 1000℃ for 1h, and then subjected to solid-phase reaction at 1600℃ for 12h to synthesize YbAG powder;

[0059] (2) Pore-forming agent mixing treatment: YbAG powder and alumina hollow microspheres 4 are placed in a mixing barrel according to the raw material mass ratio, mixed using a rolling ball mill, and uniformly dispersed by dry mixing; YSZ powder and alumina hollow microspheres 4 are dry mixed to achieve uniform dispersion.

[0060] Step 2: Pretreatment of substrate 1

[0061] The nickel-based high-temperature alloy was cut into 100 mm × 50 mm × 3 mm specifications using an electric spark cutting machine, and sandblasted with 250-mesh corundum sand. The compressed air pressure was maintained at 0.3 MPa, and ultrasonic cleaning was performed for 10 minutes after sandblasting.

[0062] Step 3: Plasma spraying

[0063] The bonding layer 2, the ceramic middle layer 3-1, and the ceramic top layer 3-2 are deposited in sequence. The specific parameters are as follows:

[0064] ① Plasma gas: Ar / H2 mixed gas, Ar flow rate is 30L / min, H2 flow rate is 10L / min;

[0065] ② Powder feeding rate: The powder feeding rate of the bonding layer 2 is 5%, and the powder feeding rate of the ceramic middle layer 3-1 and the ceramic top layer 3-2 is 13%;

[0066] ③ Spraying power: The spraying power of the bonding layer 2 and the ceramic intermediate layer 3-1 is 42kW, and the spraying power of the ceramic top layer 3-2 is 32kW;

[0067] ④Spraying distance: 100mm for each layer.

[0068] Example 2

[0069] Compared with Example 1, the difference of this embodiment is that the ceramic middle layer 3-1 contains 3 wt% of alumina hollow microspheres 4, and the ceramic top layer 3-2 contains 3 wt% of alumina hollow microspheres 4. The rest is the same as Example 1.

[0070] Example 3

[0071] Compared with Example 1, the difference of this embodiment is that the ceramic middle layer 3-1 contains 4 wt% of alumina hollow microspheres 4, and the ceramic top layer 3-2 contains 4 wt% of alumina hollow microspheres 4. The rest is the same as Example 1.

[0072] Example 4

[0073] Compared with Example 1, the difference of this embodiment is that the ceramic middle layer 3-1 contains 5wt% of alumina hollow microspheres 4, and the ceramic top layer 3-2 contains 5wt% of alumina hollow microspheres 4. The rest is the same as Example 1.

[0074] Comparative Example 1

[0075] Compared with Example 1, the difference of this comparative example is that the pore-forming agent alumina hollow microspheres 4 are not added to the ceramic middle layer 3-1 and the ceramic top layer 3-2, and the rest is the same as Example 1.

[0076] Comparative Example 2

[0077] Compared with Example 1, the difference of this comparative example is that the pore-forming agent alumina hollow microspheres 4 are not added to the ceramic intermediate layer 3-1, and the rest is the same as Example 1.

[0078] Comparative Example 3

[0079] Compared with Example 1, the difference of this comparative example is that the pore-forming agent alumina hollow microspheres 4 are not added to the ceramic top layer 3-2, and the rest is the same as Example 1.

[0080] Comparative Example 4

[0081] Compared with Example 1, the difference of this comparative example is that the pore-forming agent is graphite, and the rest is the same as Example 1.

[0082] Example 5

[0083] This embodiment provides a dual-ceramic-layer thermal barrier coating, comprising the following components:

[0084] Substrate 1 is nickel-based high-temperature alloy, model GH3536;

[0085] Adhesive layer 2, NiCrAlY adhesive layer, 80 μm thick;

[0086] The ceramic intermediate layer 3-1 is a YSZ layer containing 2 wt% alumina hollow microspheres 4, with a thickness of 150 μm;

[0087] The ceramic top layer 3-2 is LaMgAl containing 2wt% alumina hollow microspheres 4 11 O 19 layer, thickness 150 μm;

[0088] The thermal expansion coefficient of each functional layer has a gradient from the substrate to the surface;

[0089] The particle size of NiCrAlY powder used is 50μm, the particle size of YSZ powder used is 100μm, and the particle size of LaMgAl 11 O 19 The powder particle size is 125 μm, and the alumina hollow microspheres 4 used have a powder particle size of 100 μm.

[0090] The specific preparation method is as follows:

[0091] Step 1: Powder preparation

[0092] (1)LaMgAl 11 O 19 Powder preparation: La2O3, MgO, and Al2O3 powders were weighed in a mass ratio of 4:1:14 and placed in a ball mill. Deionized water was added to the mill at a water:powder ratio of 2:1. Zirconia grinding balls (10 mm and 5 mm diameter, 1:1 mass ratio) were added to the mill at a total ball:powder / water ratio of 1:1. The mill was then placed in a roller mill and milled for 24 hours. The milled slurry was poured into a stainless steel container and spray-dried. The spray-dried mixed powder was placed in a corundum dry pan and calcined in a box furnace at 1525°C for 12 hours. The mixture was then cooled, allowing a high-temperature solid-phase reaction to form the product, LMA.

[0093] (2) Pore-forming agent mixing treatment: LaMgAl 11 O 19 The powder and the hollow alumina microspheres 4 are mixed by dry method to achieve uniform dispersion; the YSZ powder and the hollow alumina microspheres 4 are mixed by dry method to achieve uniform dispersion.

[0094] Step 2: Pretreatment of substrate 1

[0095] The nickel-based high-temperature alloy was cut into 100 mm × 50 mm × 3 mm specifications using an electric spark cutting machine, and sandblasted with 250-mesh corundum sand. The compressed air pressure was maintained at 0.3 MPa, and ultrasonic cleaning was performed for 10 minutes after sandblasting.

[0096] Step 3: Plasma spraying

[0097] The bonding layer 2, the ceramic middle layer 3-1, and the ceramic top layer 3-2 are deposited in sequence. The specific parameters are as follows:

[0098] ① Plasma gas: Ar / H2 mixed gas, Ar flow rate is 40L / min, H2 flow rate is 15L / min;

[0099] ② Powder feeding rate: The powder feeding rate of the bonding layer 2 is 7%, and the powder feeding rate of the ceramic middle layer 3-1 and the ceramic top layer 3-2 is 16%;

[0100] ③ Spraying power: The spraying power of the bonding layer 2 and the ceramic intermediate layer 3-1 is 42kW, and the spraying power of the ceramic top layer 3-2 is 32kW;

[0101] ④Spraying distance: 100mm for each layer.

[0102] The inventors conducted porosity tests on thermal barrier coatings prepared in Examples 1-4 and Comparative Example 1. SEM images of random cross-sections of the coatings were analyzed using ImageJ software to calculate the porosity. The authors found that the coating porosity increased with increasing the alumina hollow microsphere content from 2 wt% to 5 wt%. This suggests that the addition of hollow alumina microspheres can effectively increase the number of pores in the thermal barrier coating. However, excessive alumina microsphere incorporation can lead to excessively high porosity, which can affect the coating's mechanical properties. Therefore, it is important to select an appropriate pore-forming agent dosage.

[0103] In Comparative Examples 2 and 3, the inventors tried to add hollow alumina microspheres only to the ceramic middle layer / ceramic top layer, and found that Comparative Examples 2 and 3 had low porosity due to the addition of pore-forming agents to the single-layer ceramic layer, resulting in limited thermal insulation performance; it was difficult to meet the use conditions at higher temperatures.

[0104] In Comparative Example 4, the inventors discovered that replacing the alumina hollow microspheres with graphite resulted in significant losses during the thermal spraying process due to graphite's lower melting point, thus affecting pore-forming efficiency. Furthermore, graphite is easily oxidized in oxidizing atmospheres, particularly at high temperatures and in the presence of oxygen. Graphite reacts with oxygen, accelerating coating failure.

[0105] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A double-ceramic-layer thermal barrier coating, characterized in that: It comprises a substrate (1), and also comprises an adhesive layer (2) and a ceramic layer (3) deposited in sequence on the substrate (1); The ceramic layer (3) is doped with a pore-forming agent, and the pore-forming agent is hollow alumina microspheres (4).

2. The dual-ceramic-layer thermal barrier coating according to claim 1, characterized in that: The particle size of the alumina hollow microspheres (4) is 50-100 μm.

3. The dual-ceramic-layer thermal barrier coating according to claim 1, characterized in that: The ceramic layer (3) comprises a ceramic middle layer (3-1) and a ceramic top layer (3-2), wherein the ceramic middle layer (3-1) and the ceramic top layer (3-2) are sequentially deposited on the bonding layer (2), and the thermal expansion coefficients of the substrate (1), the bonding layer (2), the ceramic middle layer (3-1) and the ceramic top layer (3-2) are arranged in a gradient from large to small.

4. The dual-ceramic-layer thermal barrier coating according to claim 3, characterized in that: In the ceramic intermediate layer (3-1), the aluminum oxide hollow microspheres (4) account for 2-5 wt% of the total amount of the ceramic intermediate layer (3-1); In the ceramic top layer (3-2), the hollow alumina microspheres (4) account for 2-5 wt% of the total amount of the ceramic top layer (3-2).

5. The dual-ceramic-layer thermal barrier coating according to claim 1, characterized in that: The bonding layer (2) comprises NiCrAlY, and the thickness of the bonding layer (2) is 50-80 μm.

6. The dual-ceramic-layer thermal barrier coating according to claim 3, characterized in that: The ceramic material of the ceramic intermediate layer (3-1) includes yttria-stabilized zirconia, and the thickness of the ceramic intermediate layer (3-1) is 100-150 μm.

7. The dual-ceramic-layer thermal barrier coating according to claim 3, characterized in that: The ceramic material of the ceramic top layer (3-2) includes ytterbium aluminum garnet or ReMAl 11 O 19 One of in, The thickness of the ceramic top layer (3-2) is 100-150 μm; The ytterbium aluminum garnet or ReMAl 11 O 19 The powder particle size is 35-125μm; The Re includes one of La, Nd, Sm or Gd, and the M includes one of Mg, Zn and Mn.

8. A method for preparing a dual-ceramic-layer thermal barrier coating according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1, pretreatment of substrate (1); S2, depositing a bonding layer (2) on the substrate (1); S3, mixing a pore-forming agent with a ceramic material of a ceramic intermediate layer (3-1), and depositing the ceramic intermediate layer (3-1) containing the pore-forming agent on the bonding layer (2); S4, mixing the pore-forming agent with the ceramic material of the ceramic top layer (3-2), and depositing the ceramic top layer (3-2) containing the pore-forming agent on the ceramic intermediate layer (3-1), thereby completing the preparation of the thermal barrier coating.

9. The method according to claim 8, characterized in that The powder feeding rate when depositing the bonding layer (2) in step S2 is 5%-7%.

10. The method according to claim 8, characterized in that The powder feeding rates when depositing the ceramic middle layer (3-1) and the ceramic top layer (3-2) in steps S3 and S4 are both 13%-16%.

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